Gear transmission is the most widely used transmission and speed-changing technology. Line gear transmission pair may realize a transmission, including intersecting line gear or skew line gear at an arbitrary angle, and a high transmission ratio, and thus has advantages in applications. The previous line gear is also known as space curve meshing wheel, and the one participating in meshing in a transmission process is a pair of conjugate space curves, i.e., a pair of conjugate driving contact curve and driven contact curve; and tooth profile is circular, oval or oval ring, etc. The tooth profile moves along the contact curve to form line teeth of the line gear, and the line teeth and a cylindrical wheel body constitute the line gear. The line gear with such structure may obtain a high shape precision by adopting laser rapid prototyping technology. In order to achieve a better processing efficiency, numerical control machining method may be adopted to machine the line gear. However, since the line tooth of the aforesaid line gear has a spatial cylinder structure, and forms a cantilever beam structure with the wheel body, vibration occurs in the numerical control machining, resulting in a poor machining precision of the line teeth, and an insufficient bending strength of a tooth root. Accordingly, it is necessary to rationally change and optimize the line teeth structure of the line gear for the numerical control machining of the line gear. The present invention proposes a line gear with optimally designed line teeth, which is similar to an ordinary cylindrical gear except that the meshing theory is a pair of conjugate space curves meshing, and that two meshing tooth profile curves are inscribed in two circular arcs at a meshing point. The optimally designed line gear has high contact strength and bending strength, is easier to be numerical control machined, and is easier to be mass-produced.